class ListNode{
    public int val;
    public  ListNode prev;
    public  ListNode next;
    public  ListNode(int val){
        this.val=val;
    }
}
public class MyLinkedList {
    public ListNode head;
    //带傀儡节点
    //public ListNode head=new ListNode(-1);
    public  ListNode last;
    //和单链表的打印方式是一样的
    public void display(){
        ListNode cur=this.head;
        while(cur!=null){
            System.out.print(cur.val+" ");
            cur=cur.next;
        }
        System.out.println();
    }
//得到单链表的长度
    public  int size(){
        int count=0;
        ListNode cur=this.head;
        while(cur!=null){
            count++;
            cur=cur.next;
        }
        return count;
    }
//查找是否包含关键字key是否在单链表中
    public boolean contains(int key){
        ListNode cur=head;
        while(cur!=null){
            if (cur.val==key){
                return true;
            }
            cur=cur.next;
        }
        return false;
    }
//头插法
    public void addFirst(int data){
        ListNode node=new ListNode(data);
        if (this.head==null){
            this.head=node;
            this.last=node;
        }else{
            node.next=this.head;
            head.prev=node;
            this.head=node;
        }
    }
//尾插法
    public void addLast(int data){
        ListNode node=new ListNode(data);
        if (this.head==null){
            this.head=node;
            this.last=node;
        }else{
            this.last.next=node;
            node.prev=this.last;
            this.last=node;
        }
    }
//删除第一次出现关键字为key的节点
    public void remove(int key){
        ListNode cur=this.head;
        while(cur!=null){
            if (cur.val==key){
                if (cur==head){
                    head=head.next;
                    head.prev=null;
                }else{
                    cur.prev.next=cur.next;
                    if (cur.next!=null){
                        //中间位置
                        cur.next.prev=cur.prev;
                    }else {
                        last=last.prev;
                    }
                }
                return;
            }
            cur=cur.next;
        }
    }
//删除所有key的节点
    public void removeAllKey(int key){
        ListNode cur=this.head;
        while(cur!=null){
            if (cur.val==key){
                if (cur==head){
                    head=head.next;
                    head.prev=null;
                }else{
                    cur.prev.next=cur.next;
                    if (cur.next!=null){
                        //中间位置
                        cur.next.prev=cur.prev;
                    }else {
                        last=last.prev;
                    }
                }
                //return;
            }
            cur=cur.next;
        }
    }


    public ListNode searchIndex(int index){
        ListNode cur=this.head;
        while(index!=0){
            cur=cur.next;
            index--;
        }
        return cur;
    }
//任意位置插入，第一个数据节点为0号下标
    public void addIndex(int index,int data){
        ListNode node=new ListNode(data);
        if(index<0||index>size()){
            System.out.println("index位置不合法！");
            return;
        }
        if (index==0){
            addFirst(data);
            return;
        }
        if (index==size()){
            addLast(data);
            return;
        }
        ListNode cur=searchIndex(index);
        node.next=cur.prev.next;
        cur.prev.next=node;
        node.prev=cur.prev;
        cur.prev=node;
    }
//清空
    public  void clear(){
        while(head!=null){
            ListNode curNext=head.next;
            head.next=null;
            head.prev=null;
            head=curNext;
        }
        last=null;
}


















}
